The broad goal of this program is to develop a more complete understanding of the mechanisms responsible for the vascular changes in hypertension and in the sequelae of hypertension. The studies proposed are based on results of our first research period, on important recent findings in hypertension research throughout the world and on the particular expertise of local investigators in the field. Our strategy is one of monitoring all relevant variables during the development of hypertension in order to define the complete sequence of events leading from the introduction of an intervention to the resultant vascular change that causes the elevation of arterial pressure. The overall problem will be studied at three levels: 1. Vascular smooth muscle contraction, with emphasis on cell membrane permeability, 2. Hemodynamics and local circulation, and 3. Endocrine and nervous control. At all levels special attention will be given to the role played by sodium.